What are the matching rules for C++ function overloading?

C function overload matching rules are as follows: match the number and type of parameters in the call. The order of parameters must be consistent. The constness and reference modifiers must match. Default parameters can be used.

Matching rules for C function overloading

Function overloading is a method in C that allows functions to have the same name but different parameter lists characteristic. When the compiler encounters a function call, it uses a set of rules to determine which overloaded function to call.

Matching rules:

1. Best match first principle: The compiler first looks for a function that exactly matches the call. If there are multiple matches, the most specialized match (i.e. the one with the most specific parameter type) is chosen.
2. Number and type of parameters: The name of the function and the number of parameters must match. If the parameter types do not match, the compiler attempts a type conversion.
3. Parameter order: The order of arguments to a function must match the order in the call.
4. Matching of constness and references: const and references must match the modifiers in the call.
5. Default parameters: If a function has default parameters and the corresponding parameter is not provided in the call, the compiler will use the default value.

Practical case:

Consider the following function overloading:

void print(int value);
void print(double value);
void print(const char* str);

The following call example:

print(42);  // 调用 int 重载
print(3.14); // 调用 double 重载
print("Hello"); // 调用 char* 重载

// 报错：无法将 int 隐式转换为 char*
// print(42, "Hello");

// 报错：参数顺序不匹配
// print("Hello", 42);

Conclusion:

The matching rules for C function overloads help the compiler determine which function overload to execute when called. Following these rules ensures that you get the expected behavior when using overloaded functions.

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